I'm playing on normal difficulty

When I played him on Hard, I saved up all my sweet Elixirs for him and other food to get a lot of stat boosts. Whenever he used Mirage, I would just use my Shadow Guardian to make it even. Also, when he uses his move that stuns him and then heals him over time, just go crazy on him. I think I had about 150 max focus too from items like the robes you get in the area with like 5 people defending it. So Soul Shatter hit for wicked amounts at full focus. I tried to use my 'energy field' move away from him so that he wouldn't be stunned and I'd be able to hit him with four Soul Shatters, all at 150 focus from the rapid regeneration energy field gives you. Hope this helps :)

Kazuro with a Priest on Normal? Considering I've just wasted the fellow about 10 or more times farming for stuff (No idea why, his stuff is useless for Priests.), here's how I go about it.

I use a combination of Ice Spikes and the first shadow shot ability, usually it goes 1 Ice Spike and 2 Shadow shots, by this point he's managed to reach me, if he prepares shockwave, Blink.

If he pulls out his Shadow Puppets, throw a Shadow Guardian, on Normal the 1-point Guardian should be enough to keep it distracted. You can also do the same if Kazuro's chasing you across the area, they'll be killed quite quickly, but the point is to have Kazuro not on you anyway.

For Ultimates, I use Force Field defensively if I can't Meditate quickly enough. Meditate is saved for when I've frostied him and I can recharge and make a run for it or I need healing, save the Dark Potion for if you need healing and Force Field is on cooldown.

If he's in Dark Prayer mode use Force Field over Meditate since you don't want to give him time to heal when you Meditate, bombard him with spells, especially the ice spikes so if he gets moving, he's going to be on the slow side and you can still pepper him a bit before you go back to running to the other side of the map.

here's a simpler version of cryo's strat.

-Main idea is to have Energy Field, Soul Shatter, Meditate, Blink. Then max intel & damage boosts.

-Use Ice Spikes initially, run, use energy field and cast Soul Shatter 3-4 times. If you have high focus (I have 180 on my non premium priest) you hit about 3k a pop. Energy field restores your focus for a short times, so you'll hit ~10-12k with 4 soul shatters.

-Use blink and ice spikes to avoid him until Energy field's cooldown is over. Repeat. Should only take 2 barrages.

Notes:
-If he flies, kill his minion and use meditation and wait.
-If he stuns himself, just unleash soul shatters. They do 4-5k a pop when he's self healing. You can do 20k+ damage to him then. Considering he has 22kish total health, easy.
-To get 180 focus: Fancy Robe, Eye of Naga, Maxed Focus Skill

Hope that helps! You can use the same strat on any other boss in the game and 1-shot them.

i used ghost shurikens and if my focus is almost out (at least left 50 focus) then i call shadow guardian and while kazuro attack shadow guardian, use meditate and if kazuro chase you use ice shard to make slow and if the ghost shuriken already full use it and do that again, again and again

My equip: I kept the robes that gave 20 focuses and 55 intellect (find them at the last warlord's place), instead of using them to complete the quest. I also used skill points to increase my focus by 30. So I had 150 focus.
I found the naga eye to increase my focus by 30 again to 180, but I didn't use that when I fought kazuro..

In the battle:
I used 1 shadow, then went to the side.

Used force field to generate a quick sp regen field, then spammed the attack that uses your sp to generate how much damage you do. I made sure to only attack when focus was at 110 -120 at least. I finished him off in about 15 seconds... In my 2nd attempt.

Kinda op but it works. I've heard it doesn't work well for the bonus levels though.